This invention relates generally to material deposition apparatus, and more particularly to an evaporation source used in a RF evaporation apparatus and to a process for the self fractionation deposition of a metallic layer on a workpiece.
Evaporation apparatus is well known in the art. U.S. Pat. No. 3,401,055 to J. L. Langdon et al, issued Sept. 10, 1968, and assigned to the IBM Corporation, describes how such evaporation apparatus is used in semiconductor integrated circuit processing technology. Specifically, this patent teaches a method of depositing a metal such as a solder onto a plurality of small areas simultaneously on a semiconductor device.
As semiconductor integrated circuit chips have become denser, i.e., a million or more semiconductor devices per chip, evaporated films must meet more exacting criteria. Specifically, the films must have a thickness that does not appreciably vary either across one wafer or wafer to wafer, and the amount of conductivity-detracting impurities such as oxides must be kept at a minimum.
Using the evaporation apparatus and techniques of the prior art, for example as in the above identified U.S. Pat. No. 3,401,055, fabrication of a uniform formation of high quality thin films of low vapor pressure materials (e.g. copper) is extremely difficult. Thus, there is a need in the art for an evaporation apparatus that can efficiently deposit low vapor pressure metallic films.